Petroleum System Modeling of Devonian Duvernay Formation, Western Canada Sedimentary Basin: Implication for Shale Oil and Gas Resources

Abstract

Industrial data from recent pilot production wells suggested the Devonian Duvernay shale play is one of the best liquid-rich plays in the Western Canada Sedimentary Basin. Studies indicate that nano-metre scale pores exist in the organic matter as a result of thermal decomposition of kerogen in the organic-rich shales. SEM images from a series of organic-rich and thermal mature core samples of Duvernay Formation provide visual support for the belief that organic pores may host a large amount of hydrocarbons. This study examines the hydrocarbon resource potential through a mass balance approach by using petroleum system modeling to simulate the burial, thermal maturity, hydrocarbon generation and expulsion histories as well as their spatial variations in the Duvernay Formation. Organic porosity was then calculated and oil and gas resource potentials were estimated. A correction of the amount of adsorbed gas by considering its occupation of pore space was performed. The modelling results show that: 1) kerogen conversion to hydrocarbon in Duvernay shale completed at vitrinite reflectance of 1.2 -1.4 %Ro, with oil generation and expulsion rates increasing dramatically from vitrinite reflectance %Ro 0.8 to 1.0 and %Ro 0.78 to 0.84, respectively; 2) organic porosity associated with the conversion of solid kerogen to hydrocarbon can be up to 8% in Duvernay Formation, with a medium value of 4.5%; 3) the abundance of adsorbed and free-gas resources in organic pores varies spatially in the central Alberta depending on thermal maturity and initial TOC content. The estimated median value of total natural gas in-place is 404.8 TCF and the median value of in-place shale oil resource is 81420 MMbbl, which are comparable with ERCB's assessments in 2013.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016